Non-evaporative drying method



United States Patent 3,384,971 NON-EVAPORATIVE DRYING METHOD Leo J. Thomas, Jr., and Forrest A. Richey, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed June 11, 1965, Ser. No. 463,321 Claims. (Cl. 34-9) This invention relates to a method for removing diffusible liquids from permeable solids such as hydrophilic colloid layers by the use of high molecular weight materials. One of its more specific aspects relates to a method of drying hydrophilic colloid layers of photographic products.

Previously, permeable solid materials containing diffusible liquids have in general been dried in one or another of two different ways both of which involve evaporation (1) by evaporative drying or (2) by immersing the permeable solid material in an extractant for the diffusible liquid therein in which the residual extractant is removed by evaporation.

Evaporative methods of removing diffusible liquids have not proven to be particularly suitable where a considerable amount of solids or other non-volatile materials are present since a residue of the non-volatile material may be left even if the diffusible liquid has been removed. These previous methods ordinarily required auxiliary features such as forced air circulation, vacuum centrifuging, or other additional factors which add to the cost and difficulty involved.

An object of our invention is to provide a non-evaporative method of removing diifusible liquids from hydrophilic colloid layers containing same. Another object of our invention is to provide a process for removing diffusible liquids from hydrophilic colloid layers as found in photographic products in which substantial removal of non-volatile impurities also occurs. Other objects of our invention will appear herein.

In its broadest aspects, our invention relates to the removal of diffusible liquids from permeable solid materials by contacting said permeable solid material with a polymer having an average molecular weight of at least 900, said polymer being at least 30% soluble, by weight, in said diffusible liquid and substantially non-diffusing into said permeable solid material. The polymer employed as the drying agent can be either employed as such, or it can be employed in admixture with various liquids providing that it contains no more than 400% by weight (based on the polymeric drying agent) of the diffusible liquid which 7 is removed from the permeable solid material being dried.

Many of the polymeric drying materials effective for drying the permeable solid material are solid in nature and they can either be used in that form or they may be used in liquid condition as a melt or as a solution in a solvent, the whole or part of which solvent may be diffusible liquid like that to be removed from the permeable solid material. In the case of the drying agents which are liquid, they may be used either in that form or in the form of a solution for drying the permeable solid material. The drying may be accomplished at various temperatures, the maximum of which is limited only by the temperature at which the permeable solid material being dried is disintegrated. In some cases temperatures on the order of 100-15 0 F. render the drying operation more effective.

Our invention is particularly useful, because of its quickness, in drying of layers of permeable solid materials having thicknesses dry of limited amounts such as -100 microns. In the case of layers of greater thickness more drying time is necessitated although even in the case of those layers time is saved over evaporative drying and 3,384,971 Patented May 28, 1968 any possibility of case hardening such as might be encountered with evaporative hardening is avoided.

In contacting permeable solid layers with liquids there is penetration of the liquid into the solid layer. As an example, in the case of hydrophilic layers present in photographic products, those layers are swollen by contacting with aqueous solutions such as in the processing of those photographic products. In the coating out of hydrophilic colloid layers onto a support from their solutions, drying of the layers is desirable. In many situations time is saved by using the drying method of the invention as compared to the use of evaporative drying.

The drying operation in accordance with the invention may be carried out by contacting the permeable solid layer containing ditfusible liquid with the drying agent in some manner. If the drying agent is a solid, the layer of permeable solid material may be passed over a block of the drying agent which may for instance be in the form of a rotating or non-rotating cylinder. As another alternative, the permeable solid material containing diffusible liquid can be contacted with the drying agent by immersing in a composition of the drying agent in liquid form such as in an aqueous system containing equal parts of water and drying agent. Various means of contacting the drying agent and the permeable solid material to be dried will occur to the individual operator according to his convenience.

Although our invention is useful for removing diffusible liquids from permeable solid materials generally, it is especially useful for those situations in which the diffusible liquid is aqueous and the layer to be dried is a hydrophilic colloid as is often encountered in preparing photographic products and processing those products. For instance where a photographic emulsion layer is processed with a quick developing bath and quick drying is desired the photosensitive emulsion layer after processing may be led into immediate contact with the drying agent in accordance with the invention thereby removing not only water but salts or other materials which may be in solution in the water. If the photographic product is dried by immersion in an aqueous solution of the drying agent on the product as it comes from the drying bath and containing salts or the like may be squeegeed off or by some other convenient means of wiping the surface of the product. If the product to be dried is one wherein the image is transferred from the active surface, such as from a photographic emulsion to a nucleated receiving sheet, our invention may be conveniently employed by passing the surface of the receiving sheet over a block of the drying agent or, as an alternative the receiving sheet may be contacted with the drying agent in liquid form after which the surface liquid may be squeegeed off or otherwise removed. In the case of a freshly coated photographic product, the layer of hydrophilic colloid may be set such as by chilling or fuming with ammonia in the case of gelatin layers and the water and dissolved materials may be conveniently removed in accordance with the invention by contacting with the drying agent in some manner as specified above.

The following organic materials are useful as drying agents in accordance with our invention and are particularlyuseful in removing diifusible liquids of an aqueous nature from a liquid-containing permeable solid material:

(1) Polyethylene glycols (ordinarily mixtures) having an average molecular weight of 90020,000, represented by the formula HOC H (OC H OH such as those marketed by Union Carbide & Chemicals Corp. under the trade name Carbowax.

(2) Degraded gelatin having an average molecular weight of 900-10,000;

(3) Polyacrylamides having an average molecular weight within the range of 9005,000;

(4) Polyvinyl pyrrolidones having an average molecular weight of 900-40,000;

(5) Alkylene oxide-silicone copolymers marketed by Union Carbide & Chemicals Corp. under the trade name Silicone polymers L520, L530, etc.;

(6) Ethylene oxide-propylene oxide copolymers in which ethylene oxide constitutes at least 40% of the polymer and having an average molecular weight of 900 up to 20,000 marketed under the trade name Pluronic by Wyandotte Chemical Co.;

(7) Polyvinyl alcohols having an average molecular weight of 9005,000;

(8) Urethane polyether resins having an average molecular weight of at least 900 such as those marketed by Dow Chemical Co. under the trade name Voranol;

(9) Polyacryloxy sulfonic acids having an average molecular weight of at least 900;

(10) Vinyl ether-maleic anhydride copolymers having an average molecular weight of at least 900 marketed by GAF under the trade name Gantrez resin AN1 19;

(11) Branched chain polymers having an average molecular weight of 900-20,000 whose structure is represented by the structural formula:

(l2) Polyethylene glycols with hydroxy groups replaced by oxy hydrocarbon groups such as methoxy, pnonylphenoxy, and the like and which have average molecular weights of at least 900;

(13) Plant gums such as gum arabic;

(14) Sucrose derivatives having an average molecular weight of greater than 900, such as octakis(2-hydroxypropyl)-sucrose, etc.

(15) Carboxymethyl cellulose.

Our invention is useful in the drying of layers of permeable solid materials. Some of the permeable solid materials, layers of which are readily dried by the procedure in accordance with our invention, are those of gelatin, polyvinyl alcohol (e.g. 88% hydrolyzed polyvinyl acetate), polyacrylamide, poly(ethylacrylate acrylic acid) (e.g. 80% ethylacrylate, acrylic acid), poly(butyl acrylate acrylic acid) (90% butyl acrylate, 10% acrylic acid) and like permeable solid materials. These layers may be coatings on various supports such as cellulose acetate film, polystyrene film, polyethylene terephthalate film,

waterproof paper, ordinary paper, aluminum or zinc sheets, glass or any conventional type support material. Furthermore, our invention has application in other areas as for example in the extraction of doping solvents from layers of permeable solid materials.

Various solvents may be employed in the practice of this invention. Water solutions of the usable compounds herein are very acceptable drying media. In addition, the alkylene oxide polymers may also be dissolved in such solvents as dioxane, dioxane-denatured alcohol, methanol, ethanol, and higher alcohols. Water may also be used in combination with the above listed solvents. However, our invention is not to be limited by the use or choice of solvents.

Other compounds may also be added to the drying baths of our invention for various purposes, for example, a hardener such as formaldehyde or mucochloric acid may be added to the drying bath. Such compounds would diffuse into the film to harden the hydrophilic colloid during the drying treatment. Stabilizing agents such as thiourea may also be used in the drying baths. This type of compound also dilfuses into the film during the drying treatment to stabilize the silver image in the film. Other compounds which can be added to the drying baths of our invention are dye-stabilizing agen s, Such comp un s are useful in stabilizing color images and are imbibed into the color film during the drying treatment.

The surfaces of the films and webs dried in accordance with our new and improved drying procedure are sulficiently free of any residual drying agent so that the film surface may be given a further coating of, for example, lacquers, lubricants, etc.

The molecular weights designated of the polymers are to be understood as average molecular weights for instance in the case of polymers in which the average molecular weight is designated as 900, 1000, 1500, or the like, there are often polymers present whose molecular weight may be no more than 200 or 300. These polymeric units are of little if any assistance in drying the permeable layer but in many cases they are responsible when used in the drying agent for photographic emulsion for imparting increased covering power to the emulsion.

The following examples illustrate our invention but it is to be understood that they are not limiting thereof.

Example 1 A photographic film composed of a layer of gelatinsilver halide photographic emulsion, the emulsion layer being of approximately 25 microns thickness was exposed and was processed in a processing solution composed of hydroquinone, metol, sodium carbonate, sodium sulfite, sodium thiosulfate and water. Due to the absorption of solution the emulsion layer became approximately 95 microns thick. The film was removed and immediately immersed in an aqueous 50% solution of Carbowax 6000 and was held for 40 seconds with agitation. The film was removed and squeegeed. The film was sensibly dry and the thickness of the emulsion layer had been reduced by approximately the original dry thickness. The photographic image was found to be stable indicating that the drying treatment had removed not only the water but also dissolved reagents such as developing and fixing agents from the film. This procedure was repeated using other proportions of Carbowax to water as for example 40:60, :20, 30:70, etc., and substantially the same results were obtained. In other instances the processed film was first washed with water and then dried in the manner described. The same results were obtained. Other Carbowaves having molecular weights varying from 900 to 20,000 were used and comparable results were obtained.

Example 2 Processed film was dried as described in Example 1 but by immersing in a mixture of polyvinyl pyrrolidone and water in equal proportions and squeegeeing the polyvinyl pyrrolidone having a molecular weight of approximately 40,000. The emulsion layer which had been swollen to approximately microns in processing was upon drying reduced to substantially the same thickness as prior to processing, and was sensibly dry. Salts of other water soluble reagents which might otherwise have been present were substantially eliminated. Other proportions of polyvinyl pyrrolidone and water such as aqueous solutions of polyvinyl pyrrolidone of from 30% to 80% concentration were used in like manner and like results were obtained. In other runs polyvinyl pyrrolidones of various molecular weights from 900 up to 40,000 were employed and good drying effects on wet film were obtained. Also samples in which the film had been processed and was then washed in water were dried using mixtures of polyvinyl pyrrolidone and water in like manner. Good drying was obtained.

Example 3 A procesed film composed of a gelatin-silver halide emulsion layer on a film support was dried in an aqueous solution if a polyethylene glycol-polypropylene glycol copolymer in which the ethyene glycol and propylene glycol were copolymerized in the ratio of 80:20 which copolymers had an average molecular weight of 4500. Results similar to those in Example 1, where Carbowax was used as the drying agent, were obtained. Also when varying proportions of copolymer to water and .copolymers of varying molecular weights such as within the range of 900 to 20,000 were used similar results were obtained. When like copolymers but resulting from other proportions of polyethylene glycol and polypropylene glycol were used similar results were obtained. The copolymers used in each case were Water soluble.

Example 4 The drying method described in Example 1 was repeated except that a branched-chain polymer having a formula represented by the following:

and having an average molecular weight of 1100 was used instead of Carbowax. Drying effects similar to those described in Example 1 were obtained. These polymers were also used in varying molecular weights and with varying proportions of polymer and water such as those having average molecular weights of at least 900. Also aqueous solutions containing from 3080% of polymer were used in various runs and good drying effects were obtained.

Example 5 Samples of film in which the emulsion layer was in swollen condition due to processing in aqueous solutions were dried with Carbowax sans water. In the case of those Carbowaxes which were liquid the film was immersed therein and squeegeed in the same manner as de scribed in Example 1. In the case of solid Carbowaxes such as Carbowax 6000 and the like the Wet film was passed over a smooth block of the Carbowax and similar results were obtained namely that substantially all of the water and any dissolved salts therein were removed from the photographic emulsion layer.

Example 6 A gelatin-silver halide photographic emulsion was coated onto a film base and was set by chilling. The film thus obtained was then immersed in a solution of one part of Carbowax 1540 (average molecular weight 1540) and two parts of water at 70 F. for 30 seconds and the film was then sque-egeed. The resulting product was sensibly dry substantially all the water had been removed from the emulsion layer. Other photobraphic films freshly prepared and set by chilling were dried in like manner using various concentrations of drying agents and water and similar results were obtained.

Example 7 Freshly separated and presoaked films as described in pending US. application Ser. No. 835,473 of Tregillus filed Aug. 24, 1959, in which the matrix contains the negative silver image and the positive silver image is in a layer upon a support were passed through liquid Carbowax 1540 at l80-2l0 F. and were squeegeed upon exit therefrom. The films were sensibly dry and could be wound and rewound without damage to the layers.

It may be desirable in some cases to include in the drying composition when used in liquid form, a latex. Some latices which can be incorporated in the liquid drying compositions of the invention are ethyl acrylateacrylic acid copolymer latex, butyl acrylate-acrylic acid copolymer latex or the like in minor amounts without adversely affecting the drying properties of the active agents therein.

The invention has been described in considerable detail with particular reference to certain preferred embodimeats thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. A non-evaporative process for removing dilfusable liquid from a permeable solid material which comprises contacting said permeable solid material with a drying medium composition containing (a) at least about 20% by weight of an organic material having an average molecular weight of at least about 900, and being at least 30% soluble by weight in said ditfusible liquid and substantially nondilfusible into said permeable solid material, and (b) O-400% by weight (based on said organic material) of said diffusible liquid and then removing said drying medium composition from contact with said permeable solid material, after said drying medium composition had removed a substantial amount of said diffusible liquid from said permeable solid material.

2. The process as defined in claim 1 wherein said diffusible liquid is water and said permeable solid material is a water-permeable hydrophilic colloid.

3. The process as defined in claim 1 wherein said organic material is a polyethylene glycol.

4. The process as defined in claim 1 wherein aid organic material is a degraded gelatin.

5. The process as defined in claim 1 wherein said or ganic material is a polyacrylamide.

6. The process as defined in claim 1 wherein said organic material is a polyvinyl pyrrolidone.

7. The process as defined in claim 1 wherein said organic material is an ethylene glycol-propylene glycol copolymer. 7

8. The process as defined in claim 1 wherein said organic material is a branched chain polymer comprising polyalkylene units attached to a glycerin residue by ether linkages.

9. The process as defined in claim 1 wherein said diffusible liquid is water, said permeable solid material is gelatin, and said organic material is a polyethylene glycol.

10. The process as defined in claim 1 wherein said organic material is in a solid state.

11. The process as defined in claim 1 wherein said contacting is effected by passing said permeable solid material over a cylinder having a surface of said organic material.

12. The process as defined in claim 1 wherein said contacting is elfected by immersing said permeable solid material in an aqueous solution of said polymeric material.

13. The process of drying wet, swollen exposed and developed photographic emulsion layers which comprises contacting said layers with polyethylene glycol having an average molecular weight within the range of 900-20,000.

14. The process of drying wet, swollen photographic emulsion layers which comprises contacting said layers with an aqueous solution of polyethylene glycol having an average molecular weight within the range of 90020,000.

15. The process of drying wet, swollen photographic emulsion layers which comprises contacting said layers with an aqueous solution of polyethylene glycol having an average molecular weight of 6,000.

16. The process of drying wet, swollen photographic emulsion layers which comprises contacting said layers with a 50% aqueous solution of polyethylene glycol having an average molecular weight within the range of 900- 20,000.

17. The process of drying wet, swollen photographic emulsion layers which comprises contacting said layers with a 50% aqueous solution of polyethylene glycol having an average molecular weight of 6,000.

18. The process of drying wet, swollen gelatin layers which comprises contacting said layers with a polyethylene glycol having an average molecular weight within the range of 900-20,000.

19. A nonevaporative process for drying water-wet, hydrophilic colloid layers of exposed and developed photographic products which comprises contacting said layers with a drying medium composition containing at least 20% by weight of an organic material having an 7 8 average molecular Weight of at least about 900 and be- 2,917,833 12/1959 Kremen et al. 349 ing at least 30% by weight soluble in water and substan- 3,292,271 12/1966 Hopkins et al. 34-9 tially non-diflusible into said colloid layers.

20. The process of claim 19 wherein the organic ma- FOREIGN PATENTS terial is polyethylene glycol. 5 46 9/1963 Japan.

References Cited FREDERICK L. MATTESON, JR., Prinmry Examiner.

UNITED STATES PATENTS JOHN J. CAMBY, Examiner.

2,150,757 6/1937 Bodine 34-9 X D. A. TAMBURRO, Assistant Examiner. 

1. A NON-EVAPORATIVE PROCESS FOR REMOVING DIFFUSABLE LIQUID FROM A PERMEABLE SOLID MATERIAL WHICH COMPRISES CONTACTING SAID PERMEABLE SOLID MATERIAL WITH A DRYING MEDIUM COMPOSITION CONTAINING (A) AT LEAST ABOUT 20% BY WEIGHT OF AN ORGANIC MATERIAL HAVING AN AVERAGE MOLECULAR WEIGHT OF AT LEAST ABOUT 900, AND BEING AT LEAST 30% SOLUBLE BY WEIGHT IN SAID DIFFUSIBLE LIQUID AND SUBSTANTIALLY NONDIFFUSIBLE INTO SAID PERMEABLE SOLID MATERIAL, AND (B) 0-400% BY WEIGHT (BASED ON SAID ORGANIC MATERIAL) OF SAID DIFFUSIBLE LIQUID AND THEN REMOVING SAID DRYING MEDIUM COMPOSITION FROM CONTACT WITH SAID PERMEABLE SOLID MATERIAL, AFTER SAID DRYING MEDIUM COMPOSITION HAD REMOVED A SUBSTANTIAL AMOUNT OF SAID DIFFUSIBLE LIQUID FROM SAID PERMEABLE SOLID MATERIAL. 